It’s easy to confuse a loft conversion with loft storage but there is one major difference aside from the price. 
A loft conversion will need planning permission and building regulations whereas a non-habitable loft conversion doesn’t.
*Windows to allow in natural light 
*Added insulation to keep warm in winter and cool in summer *Fixed staircase for access
* Electrics & wiring 
*Fire safety precautions i.e. escape routes & alarms 


The loft conversion will need to have structural changes to cope with the additional weight depending on what the room is to be used for.